1. Field of the Invention
The present invention relates to telecommunications in general, and more particularly, to a method and apparatus for a self-steering antenna array.
2. Description of the Related Art
FIG. 1 is a schematic diagram of a portion of a known type of telecommunications system, designated generally as 100. Telecommunications system 100 serves a number of wireless and wireline terminals situated within a geographic area. The infrastructure of telecommunications system 100 typically comprises wireless switching center 101 (WSC) interconnected with local switching offices 103 and 105, which can provide access for wireline terminals. Toll switching office 107 advantageously interconnects local switching offices 103 and 105 and wireless switching center 101 with other local switching offices (not shown) and other wireless switching centers (not shown).
Typically, wireless switching center 101 is connected to base stations 111-114 which are dispersed throughout a geographic area serviced by telecommunications system 100. Wireless switching center 101 is responsible for, among other things, routing, or "switching," calls between wireless terminals or, alternatively, between a wireless terminal and a wireline terminal accessible to wireless switching center 101 via local and/or long distance networks.
Telecommunications system 100 is preferably envisaged to carry signals that represent any type of information (e.g., audio, video, data, multimedia, etc.) and the wireless portion of telecommunications system 100 is envisaged to support one or more wireless access technologies (e.g., Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA)) in providing one or more services (e.g., cordless, cellular, PCS, wireless local loop, SMR/ESMR, two-way paging, etc.).
The geographic area serviced by telecommunications system 100 is typically partitioned into a number of spatially distinct regions called "cells." As depicted in FIG. 1, each cell is schematically represented by a hexagon; in practice, however, each cell usually has an irregular shape that depends on the topography of the terrain and other factors. Typically, each cell contains a base station. Each base station includes antennas and radios for communicating with wireless communications terminals (e.g., wireless terminals 131-135) situated within a cell. In addition, each base station includes equipment for communicating with wireless switching center 101.
Due to variations in the field strength of the radio signals being transmitted between the wireless terminals and base stations, radio channel fading often occurs. Diversity reception is typically performed at the base stations to reduce the impairment effects of radio channel fading.
As illustrated in FIG. 2, a typical base station for performing diversity reception includes multiple reception paths. That is, an uplink signal 201 from a wireless terminal is received by antennas 203 and 205 and amplified, demodulated, and decoded by radio receivers 207 and 209, respectively. The received signals are input to diversity processor 211 and, in a well-known manner, diversity processor 211 processes the signals to minimize the effects of radio channel fading. The information output by diversity processor 211 is input to processing circuitry 213 where it can be further processed and conveyed to wireless switching center 101. A downlink signal from wireless switching center 101 is received and processed by processing circuitry 213 coded and modulated by radio transmitter 215 and transmitted via antenna 217 as downlink signal 219.
Although diversity reception is effective in minimizing the effects of radio channel fading, implementing such a system is costly. For example, as described above, each uplink channel requires two antennas and two complete radio receivers as well as circuitry for implementing diversity processor 211. Diversity reception thus greatly increases the cost of implementing each base station.